What type of wines/ cooking sherry do you use. I would love something more specific than a dry white wine and or a red sherry. I have had some taste really good and some really bad in what I was making and truthfully I play a type of guessing game.

for white wines, i use whatever Chablis is on sale. I don't use sherry very often except in Asian cooking, in which case it's my experiece that the soy sauce, fish sauce, ginger, garlic, or whatever else usually overpowers the taste of the sherry anyway.

We use whatever white or red wine on hand - frequently Chardonnay and Cabernet Sauvignon. Never had a drop of sherry in the house - in fact, never knowingly tasted the stuff. But I firmly believe in the "rule", if a wine doesn't taste good by itself, it won't taste good in foods.

For white, I use mostly Sauvignon Blanc, occasionally Chardonnay.
For red, I use mostly Pinot Noir, occasionally Merlot.

I'm so glad you mentioned using Merlot to cook - it's my current favorite wine and I wasn't sure...but used it in a beef stew/dumpling recipe yesterday - it was so good - started out as Rachel Rays recipe, ended up completely mine!!! which is how most recipes end up at my house!